The present invention generally relates to a warpage correcting construction for an electrical connection box and more particularly, to an electrical connection box requiring waterproofing due to its provision in an engine compartment, etc. of a motor vehicle and having a casing molded by synthetic resin, in which by correcting warpage produced on the casing, production of a gap in the casing is prevented such that waterproofing performance of the casing is improved.
In a known electrical connection box of this kind, electrical connection components such bus bars, relays connected to the bus bars, etc. are accommodated in a casing constituted by upper and lower casings molded by synthetic resin. Usually, the upper and lower casings are locked to each other such that an outer peripheral wall of the lower casing is disposed outside and below an outer peripheral wall of the upper casing.
As shown in FIGS. 1 and 2, in this prior art locking construction, for example, a locking claw 1b projecting inwardly from an outer peripheral wall 1a of a lower casing 1 and a locking claw 2b projecting outwardly from an outer peripheral wall 2a of an upper casing 2 are provided so as to be brought into engagement with each other such that the lower casing 1 and the upper casing 2 are locked to each other.
In case the above mentioned electrical connection box is provided in an engine compartment of a motor vehicle, water readily penetrates into the electrical connection box. Therefore, the electrical connection box is required to be not only waterproofed but arranged to easily drain penetrated water outwardly. Thus, various measures for waterproofing and drainage have been taken for the electrical connection box.
For example, when an upper cover 3 is further mounted on the lower casing 1, a rubber seal 4 is provided between an upper edge 1c of the outer peripheral wall 1a of the lower casing 1 and the upper cover 3.
Each of the lower casing 1 and the upper casing 2 is formed through integral molding by using molds. However, in the lower casing 1 in which the outer peripheral wall 1a extends up to a considerable height from an outer peripheral edge of a bottom wall and an upper end of the lower casing 1 is open, the outer peripheral wall 1a is likely to warp inwardly. Especially, at a portion of the outer peripheral wall 1a above the locking claw 1b for its engagement with the upper casing 2, this warpage of the outer peripheral wall 1a increases. Furthermore, if the outer peripheral wall 1a has a long side, warpage of the outer peripheral wall 1a increases at a central portion of the long side.
Warpage of the outer peripheral wall 1a is produced mainly by the following cause. Namely, when the lower casing 1 is molded by filling synthetic resin between an inner mold and an outer mold, the inner mold reaches high temperature but the outer mold is held at relatively low temperature. By this temperature difference between the inner mold and the outer mold, the outer peripheral wall 1a of the lower casing 1 warps inwardly as shown in FIGS. 3 and 4.
If the outer peripheral wall 1a of the lower casing 1 warps, it is difficult to bring the locking claw 1b of the lower casing 1 and the locking claw 2b of the upper casing 2 into engagement with each other. Meanwhile, even if the locking claw 1b of the lower casing 1 and the locking claw 2b of the upper casing 2 are brought into engagement with each other, a gap is readily produced between the lower casing 1 and the upper casing 2. Furthermore, as shown in FIG. 3, since a gap may be produced also between the lower casing 1 and the upper cover 3 in spite of the rubber seal 4, water penetrates into the electrical connection box through this gap.
In order to eliminate warpage of the outer peripheral wall 1a of the lower casing 1, it is necessary to design molds for the lower casing 1 in view of the warpage. However, since high accuracy is required for this design of the molds for the lower casing 1, production cost of the molds rises and the molds cannot be produced quickly.